Question

In a secure communication model, if an attacker intercepts a message and replaces it with a fake one before forwarding it, this attack is best classified as :

• A. Replay attack
• B. Masquerade attack
• C. Man in the middle
• D. Denial of service

Hint:

Intercept + Modify + Forward = MITM. It's the most dangerous "active" eavesdropping because the victims often don't know their conversation is being forged.

Answer 1

The Correct Option is C

Concept:
• Active security attacks involve the modification of a data stream or the creation of a false stream.
• A Man-in-the-Middle (MITM) attack occurs when an attacker secretly relays and possibly alters the communication between two parties who believe they are directly communicating with each other.

Step 1: Analyze the described attack scenario
The attacker:
• Intercepts a legitimate message in transit.
• Replaces the original message with a fake/modified one.
• Forwards the fake message to the intended recipient. This requires the attacker to be positioned between the sender and the receiver.

Step 2: Compare with other attack types

• Replay attack: Capturing a valid message and re-transmitting it later to produce an unauthorized effect (no replacement needed).
• Masquerade attack: Pretending to be an authorized entity to gain access (usually at the start of communication).
• Denial of Service (DoS): Preventing legitimate users from accessing a service (blocking traffic, not selectively replacing it).

Step 3: Conclusion
Intercepting and replacing messages mid-flight is the textbook definition of an active Man-in-the-Middle (MITM) attack.